1) Would you use it?
No. An experienced HR rep will see straight through robotic job applications.
2) Do pilots keep an up to date application on file with dozens of airlines or do you just target a few, in which case would the time saving be enough to justify using it?
You may wish to research employment law, data protection law etc. as you may well find that "keeping applications on file" is somewhat discouraged these days in order to ensure equality and fairness. Also, you'll only be "on file" (for a short period) if you applied for an actual job posting (incase there are queries raised over the selection process for that role) .... if you just randomly sent in your CV, in most cases it will be binned.